Positioning unit, and positioning arm using the same

ABSTRACT

Provided is a unit used in a surgical operation using an endoscope, for example, to position the distal end of a surgical instrument to the region of a human body where medical treatment is required, without spreading a hole formed in the human body for insertion of the surgical instrument. This unit includes first and second output shafts pivotally connected to a movable member of the surgical instrument or the like, the first and second output shafts extending parallel to each other and being capable of reciprocating, and a drive unit for giving the first output shaft an arbitrary amount of advance/retraction and constantly giving the second output shaft an amount of advance/retraction of a constant ratio (#1) with respect to the amount of advance/retraction given to the first output shaft.

TECHNICAL FIELD

The present invention relates to a positioning unit for changing aplacement angle of a movable member and positioning a distal end thereofin a predetermined position, the positioning unit being used for, forexample, holding a surgical instrument for a surgical operation using anendoscope and to position a distal end of the surgical instrumentinserted into a human body relative to a treatment region.

BACKGROUND ART

In recent years, as a medical surgical operation to a human body, therehas been widely performed a so-called endoscopic operation in which avideo camera called an endoscope is inserted into the body and anoperation is performed with the help of a video of the inside of thebody displayed through the endoscope without opening the abdomen. In theendoscopic operation, for example, several holes of several cm areprovided in the abdomen of a patient. Treatment instruments such as theendoscope, a clamp, and a laser knife are inserted into the abdominalcavity through the holes and a trouble region in the abdominal cavity issurgically treated. According to the endoscopic operation, damage to thehuman body is small and the patient can be rehabilitated as early aspossible after the operation, as compared with the case where surgicaltreatment is performed by opening the abdomen of the patient. Therefore,the endoscopic operation has been rapidly becoming widespread in recentyears.

When such endoscopic operation is to be performed, it is necessary touse a surgical instrument which can be inserted into the human bodythrough a hole of several cm and by which treatment within the humanbody can be performed instead of by the surgeon's hands. Up to now, asthis kind of operation instrument, there has been known a surgicalinstrument as disclosed in JP 07-194608 A. Arm portions which can beopened and closed are provided at the distal end of a pipe portioninserted into the body. When the arm portions are opened and closed inthe body, the tissues of the body are held and pulled for treatment. Anoperation manipulator constructed such that the distal end of a pipeportion inserted into the body is bent back and forth like the humanwrist has been disclosed in JP 07-136173 A.

On the other hand, in the endoscopic operation, an affected treatmentarea is searched using the endoscope inserted into the human body. Then,the surgical instrument such as the laser knife or the clamp, which isinserted into the human body is approached to the affected treatmentarea. Therefore, it is necessary to move the distal end of the surgicalinstrument vertically and horizontally within the human body. However,in the endoscopic operation, the surgical instrument is inserted throughthe hole of several cm which is formed by cutting the skin and themuscle of a patient, with result that the hole is not allowed to expand.Therefore, when the distal end of the surgical instrument is to beoperated in the human body to treat the affected treatment area, it isnecessary to change a placement angle of the surgical instrument aboutthe hole formed in skin tissues to move the distal end of the surgicalinstrument up and down and sideways.

As compared with the normal operation performed by opening the abdomen,a doctor that performs the endoscopic operation must have some skill, sothat it is hard to perform the endoscopic operation by a doctor otherthan a specialist. For the patient, this means he or she can receive canreceive the endoscopic operation only in limited number of hospitalsthat employ the specialist. However, the endoscopic operation is anoperation which is performed by manipulating the surgical instrumentwhile observing a video of the inside of the body displayed on amonitor. The video obtained by the endoscope can be transmitted to adistant place through a telephone line. Therefore, if the surgicalinstrument can be suitably moved by remote control, this proves usefulbecause a specialist at a distant location can also perform theendoscopic operation and it is possible to select the endoscopicoperation from treatment methods even in a local provincial city or thelike in which the specialist does not exist.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of such problems. An objectof the present invention is to provide a positioning unit which canposition a distal end of a surgical instrument in an area to be treatedin a human body without expanding a hole formed in the body to insertthe surgical instrument, for example, in a surgical operation using anendoscope, and which can realize such positioning operation of thesurgical instrument by remote manipulation.

To attain the above object, a positioning unit according to the presentinvention includes first and second output shafts whose distal ends arepivotably connected with a movable member of a surgical instrument orthe like and which are provided parallel to each other and capable ofreciprocating; and drive means for giving an arbitrary amount ofadvance/retraction to the first output shaft and constantly giving tothe second output shaft an amount of advance/retraction at a constantratio (≠1) with respect to the amount of advance/retraction given to thefirst output shaft.

When the movable member is pivotably connected with the distal ends ofthe first output shaft and the second output shaft which are arrangedparallel to each other to thereby construct a link mechanism anddifferent mounts of advance/retraction are given to the first and secondoutput shafts, the placement angle of the movable member is changedaccording to the amounts of advance/retraction, so that the distal endof the movable member can be positioned. At this time, when an amount ofadvance/retraction at a constant ratio (≠1) with respect to the amountof advance/retraction given to the first output shaft is to beconstantly given to the second output shaft, the placement angle of themovable member is always changed about a point due to the triangularsimilitude principle. Therefore, in the case where the surgicalinstrument such as a clamp is used as the movable member, when, inholding the surgical instrument by the positioning unit of the presentinvention, a center point for changing the placement angle is alignedwith an insertion opening formed in the human body by cutting, even whenthe placement angle of the surgical instrument changes, the surgicalinstrument does not expand the insertion opening, so that the distal endof the movable member can be positioned in the area to be treated in thebody. Thus, it is possible to handle the surgical instrument withoutusing the hand of an operator, with the result that the positioningoperation of the surgical instrument can be also realized by remotemanipulation.

The positioning unit of the present invention successively changes theplacement angle of the movable member in one direction, so that thedistal end of the movable member moves only in a line. When twopositioning units are connected in series with each other to construct apositioning arm, the end of the movable member can be vertically andhorizontally moved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing how an endoscopic operation isperformed using a positioning unit of the present invention;

FIG. 2 is a perspective view showing an outward appearance of thepositioning unit to which the present invention is applied;

FIG. 3 is a perspective view showing an internal structure of thepositioning unit shown in FIG. 2;

FIG. 4 is a perspective view showing another example of a connectionportion according to an embodiment of the present invention;

FIG. 5 is a sectional view showing an internal structure of thepositioning unit shown in FIG. 2;

FIG. 6 shows a relationship between an advance and retraction ratiobetween first and second output shafts and a placement angle of asurgical instrument;

FIG. 7 is a schematic view showing an output shaft advance andretraction mechanism using racks and pinion gears;

FIG. 8 is a plan view showing a connection state between a first unitand a second unit;

FIG. 9 shows a schematic structure of a part ejection device using thepositioning unit of the present invention; and

FIG. 10 is a schematic view showing an operating state of the partejection device shown in FIG. 9.

DESCRIPTION OF SYMBOLS

10 . . . surgical instrument, 11 . . . rod, 20 . . . first unit, 21 . .. first output shaft, 22 . . . second output shaft, 21 a, 22 a . . .external thread groove, 23 . . . casing, 24 . . . first ball thread nut,25 . . . second ball thread nut, 30 . . . second unit, 50 . . . hollowmotor, P . . . patient

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a positioning unit of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 shows a state in which surgical instruments such as a clamp and alaser knife are held using a positioning unit of the present inventionand an endoscopic operation is performed while the surgical instrumentsare manipulated by the positioning unit. In the endoscopic operation,the skin of a patient P to be operated on is cut at reversal locationsby about 2 cm to 3 cm. Distal ends of surgical instruments 10 such as anendoscope 10 a serving as a video scope, a clamp 10 b, and a laser knife10 c are inserted into a human body from respective insertion openingsformed by the cutting. An operator observes a video of an affectedtreatment area in the human body, which is picked up by the endoscope 10a and displayed on a television monitor. The operator manipulates theother surgical instruments 10 b, 10 c based on a result obtained by theobservation to perform suitable treatment such as clipping of theaffected treatment area, holding thereof, or removal thereof.

In the example shown in FIG. 1, the respective surgical instruments 10are provided with rods 11 inserted into the human body. A mechanismportion 12 suited for the application of each of the surgicalinstruments 10 is provided at a distal end of each of the rods 11. Adrive portion 13 for moving the mechanism portion 12 is provided at arear end of each of the rods 11.

On the other hand, the respective surgical instruments 10 are held bythe positioning unit to which the present invention is applied. A casinghousing the drive portion 13 for each of the surgical instruments 10 isconnected with a first unit 20. The first unit 20 is connected with asecond unit 30. The first and second units 20, 30 compose a positioningarm 1 for moving the surgical instrument 10 up and down and sideways.The second unit 30 is supported by a movable arm 2 fixed to a ceiling.Therefore, the first unit 20 and the second unit 30 can be fixed at apredetermined height and a predetermined position relative to thepatient P.

FIG. 2 shows an outline of the first unit 20 and FIG. 3 shows aninternal structure thereof. The positioning unit 20 includes a firstoutput shaft 21 and a second output shaft 22 which are provided parallelto each other. The respective output shafts 21, 22 are advanced from orretracted into a casing 23 in conjunction with each other. A connectionportion 40 rotatably connected with a casing of the surgical instrument10 is provided at a distal end of each of the respective output shafts21, 22, so that the surgical instrument 10 is supported to be rockableabout axes P and Q indicated by dashed lines. Note that the connectionportion 40 may be the one provided at the distal end of the first outputshaft 21 as shown in FIG. 2 or a relatively compact one provided at thedistal end of the second output shaft 22 as shown in the drawing. Whenthe first output shaft 21 and the second output shaft 22 are advanced orretracted to provide a suitable placement angle to the surgicalinstrument 10, a distance L between the rotational axis P for the distalend of the first output shaft 21 and the rotational axis Q for thedistal end of the second output shaft 22 varies. When this is taken intoconsideration, as shown in FIG. 4, the connection portion may beprovided through a linear bearing 41 absorbing the variation.

As shown in FIG. 3, spiral external thread grooves 21 a, 22 a are formedin the first output shaft 21 and the second output shaft 22. A firstball thread nut 24 and a second ball thread nut 25 are threaded into theexternal thread groove 21 a of the first output shaft 21 and theexternal thread groove 22 a of the second output shaft 22, respectively,through a large number of balls which are endlessly circulated. As shownin a sectional view of FIG. 5, the first ball thread nut 24 threadedonto the first output shaft 21 is stored in a hollow motor 50. Thehollow motor 50 is composed of a motor housing 51 fixed to the casing 23of the positioning unit 20, a motor stator 52 fixed to the motor housing51, and a substantially cylindrical motor rotor 54 which is rotatablysupported to the motor housing 51 through a bearing 53. The first outputshaft 21 extends through a hollow portion of the motor rotor 54 and thefirst ball thread nut 24 is in fit engagement with an inner surface ofthe motor rotor 54. Therefore, when the motor stator 52 is excited torotate the motor rotor 54, the first ball thread nut 24 fixed to themotor rotor 54 rotates. The distal end of the first output shaft 21 isfixed to the surgical instrument 10, so that it cannot be rotated. Thus,when the first ball thread nut 24 rotates due to the rotation of themotor rotor 54, the first output shaft 21 advances or retracts accordingto the speed of rotation.

On the other hand, a separate motor is not provided for the second ballthread nut 25. The second ball thread nut 25 is rotated by powertransmitted through the first ball thread nut 24. A pulley 26 is fixedto an end of the first ball thread nut 24. A pulley 27 is fixed to anend of the second ball thread nut 25. A timing belt 28 is wound aroundthe pulleys 26, 27. Therefore, when the first ball thread nut 24 isrotated by the hollow motor 50, the second ball thread nut 25 rotates atthe same speed of rotation. The distal end of the second output shaft 22is fixed to the surgical instrument 10, so that it cannot be rotated.Thus, when the second ball thread nut 25 rotates, the second outputshaft 22 advances or retracts according to the speed of rotation. Notethat the second ball thread nut 25 is rotatably supported to the casing23 of the positioning unit through a support bearing 29. As shown inFIGS. 3 and 5, journal portions of the first output shaft 21 and thesecond output shaft 22 are rotatably supported to the casing 23 of thepositioning unit 20 by bearing sleeves 31 each made of resin.

In this embodiment, a lead of the spiral external thread groove 22 aformed in the second output shaft 22 is twice longer than that of thespiral external thread groove 22 a formed in the first output shaft 21.Therefore, when the first output shaft 21 is advanced or retracted dueto the rotation of the hollow motor 50, the second output shaft 22 isconstantly advanced or retracted by the amount of advance/retractionwhich is twice larger than that of the first output shaft 21. Thus, asshown in FIG. 6, a placement angle of the surgical instrument 10pivotably attached to the distal ends of the first output shaft 21 andthe second output shaft 22 is changed, with the result that themechanism portion 12 located at the distal end of the surgicalinstrument 10 can be positioned in the affected treatment area.

At this time, the rod 11 of the surgical instrument 10 rotates about apoint to change the placement angle. Such a center point O is producedin a position corresponding to a ratio between the amount ofadvance/retraction of the first output shaft 21 and that of the secondoutput shaft 22. As described in this embodiment, in the case where anadvance/retraction ratio between the first output shaft 21 and thesecond output shaft 22 is 1:2, when an interval between the first outputshaft 21 and the second output shaft 22 is d, the center point O isproduced at a position at a distance d from a pivot axis Q connectingthe first output shaft 21 with the surgical instrument 10 (see FIG. 6).This is based on a triangular similitude principle. When theadvance/retraction ratio is 1:2, the placement angle of the rod 11 ofthe surgical instrument 10 is changed about the point O where a ratiobetween a line segment OQ and a line segment OP becomes 1:2. Therefore,when the advance/retraction ratio between the first output shaft 21 andthe second output shaft 22 is constant at all times, the point O whichbecomes the center of change in placement angle of the rod 11 alwaysexists.

When the advance/retraction ratio between the first output shaft 21 andthe second output shaft 22 is to be made constant, as described above,the lead of the external thread groove 21 a of the first output shaft 21may be made different from the lead of the external thread groove 22 aof the second output shaft 22. The same lead may be used to provide aconstant ratio between the speed of rotation of the first ball threadnut 24 and the speed of rotation of the second ball thread nut 25. Whenthe number of teeth formed in the pulleys are made different from eachother in the case where torque is to be transmitted from the first ballthread nut to the second ball thread nut through the timing belt, theabove-mentioned rotation speed ratio can be easily provided.

Assume that a height of the first unit 20 is adjusted using the movablearm 2 such that the center point O is aligned with an insertion openingformed in the patient P by cutting. Here, even when the placement angleof the surgical instrument 10 is changed by the first unit 20, the rod11 of the surgical instrument 10 does not expand the insertion openingformed in the patient P. Therefore, the mechanism portion 12 located atthe distal end of the surgical instrument 10 can be positioned withrespect to the affected treatment area of the human body, withoutdamaging skin tissues and the like near the insertion opening.

Note that a structure for advancing and retracting the first outputshaft 21 and the second output shaft 22 in the first unit 20 is notlimited to a combination of the ball thread nut and the external threadgroove as described above. For example, as shown in FIG. 7, acombination of a rack and a pinion gear which are formed in each of theoutput shafts 21, 22 may be used. In this case, a first pinion gear 61engaged with a rack 60 formed in the first output shaft 21 is providedand a second pinion gear 63 engaged with a rack 62 formed in the secondoutput shaft 22 is provided. Any one of the pinion gears is rotated by amotor and torque caused by the one pinion gear is transmitted to theother pinion gear. The advance/retraction ratio between the first outputshaft 21 and the second output shaft 22 may be set such that the speedof rotation of the first pinion gear 61 is made equal to that of thesecond pinion gear 63 and reference pitches of the racks 60, 62 formedin the respective output shafts 21, 22 are made different from eachother or such that the reference pitches of the racks 60, 62 are madeequal to each other and the speed of rotation of the first pinion gear61 is made different from that of the second pinion gear 63.

In the example of the first unit 20 shown in FIGS. 3 and 5, the hollowmotor 50 is provided for only the first ball thread nut 24 and the powerof the hollow motor 50 is transmitted to the second ball thread nut 25.However, a separate motor may be provided for the second ball thread nut25. In this case, it is necessary to control the motor for driving thefirst ball thread nut 24 and the motor for driving the second ballthread nut 25 such that a ratio of amount of advance/retraction betweenthe first output shaft 21 and the second output shaft 22 and a ratio ofadvance/retraction speed therebetween are constant at all times.

On the other hand, the second unit 30 has completely the same structureas the first unit 20 and is constructed such that a third output shaft64 and a fourth output shaft 65 which are arranged parallel to eachother 22 can be advanced or retracted at a predeterminedadvance/retraction ratio. FIG. 8 is a plan view showing a connectionstate among the surgical instrument, the first unit, and the secondunit. As shown in this figure, the respective output shafts 64, 65 ofthe second unit 30 are pivotably coupled to the casing of the first unit20 through the connection portion 40. In such a coupling state, therespective output shafts 64, 65 of the second unit 30 are alwaysorthogonal to the respective output shafts 21, 22 of the first unit 20.That is, a plane including the first output shaft 21 and the secondoutput shaft 22 of the first unit 20 is always orthogonal to a planeincluding the third output shaft 64 and the fourth output shaft 65 ofthe second unit 30. When the respective output shafts 21, 22 of thefirst unit 20 are advanced or retracted, the placement angle of the rod11 of the surgical instrument 10 is changed along an X-directionindicated by an arrow line in FIG. 8. However, when the respectiveoutput shafts 64, 65 of the second unit 30 are advanced or retracted inthe above-mentioned coupling state, the placement angle of the rod 11 ofthe surgical instrument 10 is changed along a Y-direction orthogonal tothe X-direction. Therefore, when the first unit and the second unit arecoupled to each other to construct a positioning arm as shown in FIG. 8,the rod of the surgical instrument held by the first unit can be movedin the X-direction and the Y-direction. Thus, it is possible tovertically and horizontally position the mechanism portion provided atthe distal end of the rod in the human body.

In other words, when an arbitrary amount of rotation is imparted to eachof the motors of the first unit and the second unit, the mechanismportion which is located at the distal end of the surgical instrumentand inserted into the human body can be freely positioned with respectto the affected treatment area. When the motors of the first unit andthe second unit are controlled while observing a video taken by theendoscope, a specialist at a distant location can also perform theendoscopic operation.

FIGS. 9 and 10 show an example in which the positioning unit of thepresent invention is applied to another application, more specifically,a part ejection device for taking a machined mechanical part 80 such asa body part of an automobile from a jig 81 and ejecting it.

A part ejection device 70 includes a chute 71 serving as a movablemember, which is formed as a plate whose surface is smooth and lifts themachined mechanical part up from below, and an actuator unit 72 forchanging a placement angle of the chute 71, with one end of the chute 71taken as a rocking center. A unit identical to the first unit 20 shownin FIG. 2 is used as the actuator unit 72. The distal end of the firstoutput shift 21 and the distal end of the second output shaft 22 arepivotably supported to a rear surface of the chute 71. The mechanicalpart 80 is machined in a state in which it is positioned by the jig 81.During this machining, the chute 71 is set in a stand-by position shownin FIG. 9, that is, a position located below the mechanical part 80.After the completion of machining, to take out and eject the mechanicalpart 80 from the jig 81, the hollow motor 50 incorporated in theactuator unit 72 starts to rotate and then the first output shaft 21 andthe second output shift 22 are advanced from the casing 23. Therefore,as shown in FIG. 10, the chute 71 is lifted upward to take out theprocessed mechanical part 80 from the jig 81. In addition, when thehollow motor 50 rotates, the amount of advance of the first output shaft21 is different from that of the second output shift 22. Therefore, theplacement angle of the chute 71 changes at the same time it is liftedupward, so that the mechanical part 80 is ejected from the jig so as toslide down the chute 71.

At this time, when the positioning unit of the present invention is usedas the actuator unit 72, the placement angle of the chute 71 can bechanged with its one end taken as the rocking center. When a carryingdevice such as a belt conveyer is provided adjacent to the chute 71 setin the stand-by position, the mechanical part 80 ejected from the jig 81so as to slide down the chute 71 can be smoothly transferred to thecarrying device. Thus, the positioning unit of the present invention isalso useful when applied to various actuators in industrial robots andthe like.

INDUSTRIAL APPLICABILITY

As described above, according to the positioning unit of the presentinvention, the movable member is pivotably connected with the distalends of the first output shaft and the second output shaft which arearranged parallel to each other to thereby construct a link mechanism.The ratio of amount of advance/retraction between the first output shaftand the second output shaft are maintained constant so that theplacement angle of the movable member always changes about one point.Therefore, for example, in the case where the surgical instrument isheld as the movable member, even when the placement angle of thesurgical instrument changes, the surgical instrument does not expand theinsertion opening formed in the human body by cutting. Thus, the distalend of the surgical instrument can be positioned with respect to an areato be treated in the body by remote manipulation.

1. A positioning unit that holds a movable member and changes aplacement angle of the movable member to perform positioning of a distalend of the movable member, characterized by comprising: first and secondoutput shafts whose distal ends are pivotably connected with the movablemember and which are provided parallel to each other and capable ofreciprocating; and drive means for giving an arbitrary amount ofadvance/retraction to the first output shaft and constantly giving tothe second output shaft an amount of advance/retraction at a constantratio (≠1) with respect to the amount of advance/retraction given to thefirst output shaft.
 2. A positioning unit according to claim 1,characterized in that the drive means comprises external threadsrespectively formed in the first and second output shafts, a first nutand a second nut into which the external threads are respectivelythreaded, and a motor for rotating the first nut and the second nut. 3.A positioning unit according to claim 2, characterized in that a lead ofthe external thread formed in the first output shaft is different from alead of the external thread formed in the second output shaft.
 4. Apositioning unit according to claim 2, characterized in that a speed ofrotation of the first nut is different from a speed of rotation of thesecond nut.
 5. A positioning unit according to claim 1, characterized inthat the drive means comprises racks respectively formed in the firstand second output shafts, a first pinion and a second pinion which arerespectively engaged with the racks, and a motor for rotating the firstpinion and the second pinion.
 6. A positioning unit according to claim5, characterized in that a reference pitch of the rack formed in thefirst output shaft is different from a reference pitch of the rackformed in the second output shaft.
 7. A positioning unit according toclaim 5, characterized in that a speed of rotation of the first pinionis different from a speed of rotation of the second pinion.
 8. Apositioning unit according to any one of claims 1 to 7, characterized inthat the movable member is a surgical instrument for medical care andthat a distal end of the surgical instrument is positioned with respectto an area to be treated.
 9. A positioning arm that holds a movablemember and changes a placement angle of the movable member to performpositioning of a distal end of the movable member, characterized bycomprising: a first unit that holds the movable member; and a secondunit that holds the first unit, the positioning arm being characterizedin that: the first unit comprises: first and second output shafts whosedistal ends are pivotably connected with the movable member and whichare provided parallel to each other and capable of resiprocating; drivemeans for giving an arbitrary amount of advance/retraction given to thefirst output shaft and constantly giving to the second output shaft anamount of advance/retraction at a constant ratio (#1) with respect tothe amount of advance/retraction given to the first output shaft; and acasing that houses the drive means; and the second unit comprises: thirdand fourth output shafts whose distal ends are pivotably connected withthe casing of the first unit and which are provided parallel to eachother and capable of reciprocating, the third and fourth output shaftsbeing respectively orthogonal to the first and second output shafts ofthe first unit; and drive means for giving an arbitrary amount ofadvance/retraction to the third output shaft and constantly giving tothe fourth output shaft an amount of advance/retraction at a constantratio (≠1) with respect to the amount of advance/retraction given to thethird output shaft.
 10. A positioning arm according to any one of claims1 to 7, characterized in that the movable member is a surgicalinstrument for medical care and that a distal end of the surgicalinstrument is positioned with respect to an area to be treated.